OTFS mmWave Receiver for Power Amplifier Nonlinearity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional orthogonal-frequency-division-multiplexing (OFDM) modulation is unreliable in high mobility scenarios due to sensitivity to Doppler spread, and nonlinear distortions from non-ideal power amplifiers in mmWave systems complicate equalization, leading to inter-symbol interference (ISI) and intractable target distributions.
Innovation Solution
A receiver with a nonlinear detector for OTFS-based mmWave communication systems, utilizing analog beamforming, maximal ratio combining, and particle filtering to compensate for multiplicative distortions and ISI, enabling accurate delay-Doppler domain estimation through iterative MAP detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If non-ideal power amplifier is used in mmWave systems, then high power amplification is achieved, but nonlinear distortions and inter-symbol interference are introduced
Solution Approach 1:
The patent applies particle filtering to model and compensate for the nonlinear distortions generated by the power amplifier. By treating the harmful nonlinear effects as a stochastic process that can be characterized and compensated through probabilistic modeling, the system converts the harmful inter-symbol interference into a manageable statistical problem that can be resolved through iterative detection and compensation algorithms
Solution Approach 2:
The patent implements an iterative detection and compensation mechanism where the receiver detects the transmitted symbols, estimates the nonlinear distortions, compensates for them, and re-detects the symbols in successive iterations. This feedback loop progressively reduces the impact of nonlinear distortions and inter-symbol interference, allowing the system to achieve accurate detection despite the presence of power amplifier nonlinearity
2Device complexity
If conventional OFDM modulation is used, then simple modulation structure is maintained, but reliability deteriorates in high mobility scenarios due to Doppler spread sensitivity
Solution Approach 1:
The patent transitions from conventional OFDM modulation to OTFS modulation, fundamentally changing the modulation parameters and domain representation. OTFS maps data symbols onto a delay-Doppler grid rather than a frequency-time grid, changing the fundamental parameters of the modulation scheme to achieve robustness against Doppler spread while maintaining manageable system complexity through established OTFS processing algorithms
3Reliability
If OTFS modulation is used in mmWave systems, then robustness to Doppler spread is achieved, but equalization complexity increases due to two-dimensional convolution in delay-Doppler domain
Solution Approach 1:
The patent extracts and separately handles the nonlinear distortion compensation from the main equalization process. By using particle filtering to specifically address the power amplifier nonlinearities before or during equalization, the complex two-dimensional convolution equalization in the delay-Doppler domain can be performed more effectively, as the harmful nonlinear effects are independently modeled and compensated
Solution Approach 2:
The patent applies preliminary compensation for nonlinear distortions using particle filtering before performing the main equalization operation. This preliminary action prepares the signal by reducing the impact of power amplifier nonlinearities, making the subsequent equalization process more effective and potentially simpler, as the signal is pre-conditioned to be closer to linear behavior
4Device complexity
If linear power amplifier detection schemes are used, then detection simplicity is maintained, but performance deteriorates due to inability to handle nonlinear distortions
Solution Approach 1:
The patent applies particle filtering to model and compensate for the nonlinear distortions generated by the power amplifier. By treating the harmful nonlinear effects as a stochastic process that can be characterized and compensated through probabilistic modeling, the system converts the harmful inter-symbol interference into a manageable statistical problem that can be resolved through iterative detection and compensation algorithms
Solution Approach 2:
The patent implements an iterative detection and compensation mechanism where the receiver detects the transmitted symbols, estimates the nonlinear distortions, compensates for them, and re-detects the symbols in successive iterations. This feedback loop progressively reduces the impact of nonlinear distortions and inter-symbol interference, allowing the system to achieve accurate detection despite the presence of power amplifier nonlinearity
Data Source
AI summary
The present invention discloses a signal receiver and signal receiving method involving nonlinear detection method for mmWave OTFS systems in high mobility scenarios with non-ideal power amplifier, which is applicable in the fifth generation (5G) and beyond networks. The millimeter wave (mmWave) system is envisioned to be a promising candidate of 5G. However, the high frequency and large bandwidth operation in mmWaves result in nonlinear distortions from the power amplifier in the system. The nonlinearly distorted signals from non-ideal power amplifier when propagate through a wideband high mobility channel tremendously degrades the systems performance. Attributed to the non-ideal power amplifier, the nonlinear distortions induce multiplicative distortions and inter symbol interference (ISI) in the OTFS system. It further causes the posterior probability of the transmitted signal non-Gaussian and analytically intractable. The present signal receiver and signal receiving method proposes an amalgamation of maximal ratio combining (MRC) and particle filter in the delay-Doppler domain to retrieve the desired signal from the nonlinearly impaired observations.